Flight control and guidance of a vehicle through the atmosphere requires knowledge of the vehicle's motion and attitude relative to the earth's air mass. This knowledge, commonly referred to as “air data,” is generally measured using instruments that either protrude into the surrounding airstream, or are flush mounted with an outer surface of the vehicle. Alternately, other instruments may use inertial navigation system (INS) derived values.
Although desirable results have been achieved using such prior art air data systems, there is room for improvement. For example, for high-speed reentry aircraft, the use of instruments that protrude into the airstream is problematic because of the heating that occurs due to the high velocity of the air. The high velocity of a reentry aircraft means the outside surface of the aircraft experiences very high temperatures (e.g. in the 1000s of deg F). Such temperatures may be high enough to melt or break protruding instruments. Deployable probes generally require a considerable amount of calibration, are costly, and require valuable space in the aircraft near the surface to be deployed.
Air data systems that rely on flush-mounted instruments and INS-derived data also have drawbacks. For larger aircraft, flush-mounted pressure taps may be suitably positioned near the stagnation point on a relatively large curved surface. For a smaller aircraft, however, the stagnation point is typically one of the highest heating points on the aircraft, and the temperatures may be so high that flush-mounted instrumentation is impractical because the instrument materials cannot support the heating rate. Air data systems that use INS-derived data are typically too inaccurate for proper control of the reentry aircraft.
Therefore, novel air data systems and methods that provide the required accuracy and that otherwise mitigate the above-noted characteristics of the prior art air data systems would have utility.